This invention relates generally to semiconductor processing equipment and, more particularly, to a chemical vapor deposition chamber suitable for high density plasma processing.
Chemical vapor deposition (CVD) is a gas reaction process used in the semiconductor industry to form thin layers or films of desired materials on a substrate. Some high density plasma (HDP) enhanced CVD processes use a reactive chemical gas along with physical ion generation through the use of an RF generated plasma to enhance the film deposition by attraction of the positively charged plasma ions onto a negatively biased substrate surface at angles near the vertical to the surface, or at preferred angles to the surface by directional biasing of the substrate surface. One goal in the fabrication of integrated circuits (ICs) is to form very thin, yet uniform films onto substrates, at a high throughput. Many factors, such as the type and geometry of the power source and geometry, the gas distribution system and related exhaust, substrate heating and cooling, chamber construction, design, and symmetry, composition and temperature control of chamber surfaces, and material build up in the chamber, must be taken into consideration when evaluating a process system as well as a process which is performed by the system.
Some of the most widely used CVD films include tungsten, silicon dioxide, silicon nitride and polysilicon, although other CVD films suitable as insulators, dielectrics, conductors, semiconductors, superconductors and magnetics are known. The system of the present invention has been found to be particularly effective in forming thin films of doped and undoped silicon dioxide.
One problem encountered in IC fabrication is the difficulty associated with establishing a uniform plasma density over the entire substrate surface during processing. As substrate sizes increase, i.e., to 300 mm, single coil assemblies suffer wall losses and the like, thereby creating inefficient coupling of power into the plasma resulting in center peaked or cusped plasma profiles. The resulting deposition of material under non-uniform plasma densities results in films which are typically center thick or edge thick, and in either instance tend to be non-uniform.